Like grizzled miners panning for gold on a river high in the Sierras, Facebook applications developers have been toiling away, trying to figure out how to make money from the millions of people who use their apps every day. Those developers who focus on games are starting to find gold -- by which I mean revenue gained from doing things like selling virtual goods in exchange for real money.
(Note from Dave--I love the "grizzled miners" literary twist. We should start a contest to identify which techie guys were actually english majors.)